The simple tweet attracted a number of comments from those in favour of stronger gun control, with one pointing out that the Christchurch attacks, in which 51 people were killed, prompted swift legislative reform.

"The single mass shooting in New Zealand led to the immediate reform of the law (only SIX DAYS after the shooting) tightening it to ensure something like that never happens again. The US government chooses money over the lives of the American citizens."

Another highlighted the frequency with which mass shootings now occur in the US, writing: "Statistically the next one will occur 2 days from now in America."

Mourners gather for a vigil at the scene of a mass shooting in Dayton, Ohio. Picture: AP

The post also attracted a number of critics, including musician Jaymes Young who accused Mr Edwards of using selective statistics.

"Yes there's a problem but don't go spreading what's basically misinformation, you're only making the problem worse. This is as bad as the media making these murderers famous," the singer-songwriter wrote.

"Pls take a statistics class. and understand that "mass shooting" is a term, it doesn't include murders."

A mass shooting is defined as an incident in which at least four people have died during murders involving a gun, not including the shooter.

Another critic wrote: "Stupid stat. We have the second amendment. Other countries aren't allowed to carry."

The two shootings have prompted swift responses from politicians, with a number of high-profile Republicans blaming everything from mental illness to video games.

"This is mental illness," President Donald Trump told reporters. "These are really people that are very, very seriously mentally ill. So a lot of things are happening."

House Minority Leader Kevin McCarthy said video games involving shooting narratives "dehumanise" people to violence.

"I've always felt that is a problem for future generations and others," Mr McCarthy said. "We've watched from studies shown before of what it does to individuals. When you look at these photos of how it took place, you can see the actions within video games and others."

Dan Patrick, Lieutenant Governor of Texas, echoed the sentiment in saying the "video game industry … teaches young people to kill".

"You know, in this manifesto that we believe is from the shooter, this manifesto, he talks about living out his super-soldier fantasy on Call of Duty," Mr Patrick said.

"We know that the video game industry is bigger than the movie industry and the music industry combined, and there have been studies that say it impacts people and studies that says it does not, but I look at the common denominators, as a 60-some-year-old father and grandfather myself, what's changed in this country?

"We've always had guns, we've always had evil. But what's changed where we see this rash of shooting? And I see a video game industry that teaches young people to kill."

A string of other Republicans, from Vice President Mike Pence to Florida Congressman Matt Gaetz, called for prayer.

Author and journalism professor Dan Fagin took to Twitter to rebuke the claims of conservative politicians with a simple tweet of his own.

• August 4, 2019: A gunman wearing body armour shot and killed nine people at a popular night-life area in Dayton, Ohio. Police were patrolling the area and killed the suspect.

• August 3, 2019: A gunman opened fire at a shopping centre in El Paso, Texas, killing 20 people and injuring more than two dozen. A suspect was taken into custody.

• May 31, 2019: Longtime city worker DeWayne Craddock opened fire in a building that houses Virginia Beach government offices. He killed 12 people and wounded several others before he was gunned down by police.

• February 15, 2019: Gary Martin killed five co-workers at a manufacturing plant in Aurora, Illinois, during a disciplinary meeting where he was fired. He wounded one other employee and five of the first police officers to arrive at the suburban Chicago plant before he was killed during a shootout with police.

• November 7, 2018: Ian David Long killed 12 people at a country music bar in Thousand Oaks, California before taking his own life. Long was a Marine combat veteran of the war in Afghanistan.

• October 27, 2018: Robert Bowers is accused of opening fire at a Tree of Life synagogue in Pittsburgh, Pennsylvania during Shabbat morning services, killing 11 and injuring others. It's the deadliest attack on Jews in the US in history.

• June 28, 2018: Jarrod Ramos shot through the windows of the Capital Gazette offices in Annapolis, Maryland before turning the weapon on employees there, killing five at The Capital newspaper. Authorities say Ramos had sent threatening letters to the newspaper prior to the attack.

• May 18, 2018: Dimitrios Pagourtzis began shooting during an art class at Santa Fe High School in Santa Fe, Texas. The 17-year-old killed eight students and two teachers and 13 others were wounded. Explosive were found at the school and off campus.

• February 14, 2018: Nikolas Cruz shot and killed 17 students and staff members at Marjory Stoneman Douglas High School in Parkland, Florida. It surpassed Columbine High School as the deadliest shooting at a high school in US history.

• November 5, 2017: Devin Patrick Kelley, who had been discharged from the air force after a conviction for domestic violence, used an AR-style firearm to shoot up a congregation at a small church in Sutherland Springs, Texas, killing more than two dozen.

• October 1, 2017: Stephen Paddock opened fire on an outdoor music festival on the Las Vegas Strip from the 32nd floor of a hotel-casino, killing 58 people and wounding more than 500. SWAT teams with explosives then stormed his room and found he had killed himself.